The Next Generation Network (NGN) is a hot research subject of the current communication standard field, which uses packet technologies such as IP as bearer network technologies to incorporate fixed and mobile communications. The NGN can provide richer multimedia services, such as emerging services with real-time requirements (such as VoIP, video conference, multimedia tele-learning, video on demand, etc.), which require the communication networks to provide efficient end-to-end Quality of Service (QoS) support; while the requirements of users on the network QoS are also increasing. Therefore, how to provide the end-to-end QoS will be one of the core issues of the NGN.
The International Telecommunication Union-Telecommunications standardization sector (ITU-T for short) is a telecommunication sector of the International Telecommunication Union (ITU for short), which establishes a standard for resource and admission control. In the latest Resource and Admission Control Functions (RACF for short) draft promulgated by the ITU-T, a functional frame of the RACF is provided. As shown in FIG. 1, the RACF is comprised of two parts, which respectively are a Policy Decision Functional Entity (PD-FE for short) and a Transport Resource Control Functional Entity (TRC-FE), wherein, the TRC-FE interacts with the transport functions through a Rc, and interacts with the Transport Resource Enforcement Functional Entity (TRE-FE for short) through a Rn, and the PD-FE interacts with the TRC-FE through a Rt, interacts with a Customer Premises Network (CPN for short) through a Rh, interacts with a Policy Enforcement Functional Entity (PE-FE for short) through a Rw, interacts with Service Control Functions (SCF for short) of a service layer through a Rs, and interacts with Network Attachment Control Functions (NACF for short) through a Ru, and the PD-FE interacts with other NGNs through a Ri interface.
In addition, the PD-FE has nothing to do with the transport technologies, and also has nothing to do with the SCF, and the PD-FE makes the final decision on the resource and admission control based on network policy rules, service information provided by the SCF, transport-layer subscription information provided by the NACF, and results of resource availability decisions provided by the TRC-FE.
The TRC-FE has nothing to do with services, but is related to the transport technologies. The TRC-FE is responsible for collecting and maintaining transport network information and resource state information. After receiving a resource request from the PD-FE, the TRC-FE makes a resource based admission control based on the QoS, priority requirements, resource availability information, and transport related policy rules.
The transport layer is comprised of the PE-FE and the TRE-FE. The PE-FE implements policy rules issued by the PD-FE, and the PE-FE is a packet-to-packet gateway, which can be located between a Customer Premises Equipment (CPN) and an access network, between the access network and a core network or between networks of different operators, and is a key node for supporting dynamic QoS control, port address translation control, and Network Address Translator (NAT for short) traversal. The TRE-FE performs transport resource policy rules issued by the TRC-FE, and its scope and function as well as the Rn interface are to be studied further, and are not in the range of study of R2 phase.
Telecommunication and Internet converged Services and Protocols for Advanced Networking (TISRAN) presents a Resource and Admission Control Subsystem (RACS) to solve the QoS problem of a NGN bearer network from the prospective of a fixed access. The TISPAN divides the NGN architecture into a service layer and a transport layer, and introduces the RACS and the Network Attachment SubSystem (NASS) into the transport control layer. The RACS solves the QoS problem of the NGN bearer network, and the NASS is responsible for providing an upper service layer with an independent user access management. The main functions of the TISPAN RACS are similar to those of the ITU-T RACF.
The functional architecture of the TISPAN RACS is shown in FIG. 2. The RACS associates service requirements of the service layer with resource allocation of the transport layer, and mainly implements functions such as policy control, resource reservation, admission control, NAT traversal etc. The RACS provides control services of the transport layer to the service layer through a series of QoS policies, enabling the User Equipment (UE) to obtain the required QoS guarantee.
The RACS is comprised of two entities, i.e., a Service-based Policy Decision Function (SPDF) and an Access-Resource and Admission Control Function (A-RACF).
SPDF:
The SPDF provides a uniform interface to the service layer, shields the underlying network topology and the specific access type, and provides service-based policy control. The SPDF selects local policies based on a request of a Application Function (AF), and maps the request into IP QoS parameters to transmit to the A-RACF and a Border Gateway Function (BGF), to control corresponding resources.
A-RACF:
The A-RACF controls the access network, and includes admission control and network policy convergence functions, receives a request from the SPDF, then implements the admission control based on the stored policies, and accepts or rejects the request for transport resources. The A-RACF obtains network attachment information and user QoS profile information from a NASS through an e4 interface, and thus determines available network resources based on network location information (such as an address of a physical node of a access user), while refers to the user QoS profile information when processing a resource allocation request.
The transport layer includes two functional entities, i.e., a Border Gateway Function (BGF) and a Resource Control Enforcement Function (RCEF).
BGF:
The BGF is a packet-to-packet gateway, and can be located between the access network and the core network (to implement a core boarder gateway function), or can be located between two core networks (to implement an internet boarder gateway function). The BGF implements the NAT transversal, gate control, QoS tags, bandwidth limitations, usage measurement and resource synchronization functions under the control of the SPDF.
RCEF:
The RCEF performs media stream policies of layer 2/layer 3 (L2/L3) transmitted through a Re interface, and implements functions such as gate control, QoS tags, bandwidth limitations etc.
The 3rd Generation Partnership Project (3GPP) presents the Policy Control and Charging (PCC) from the prospective of a mobile access, to implement the resource and admission control function. The PCC is located between the service control layer and the access/bearer layer, and implements a certain QoS control mechanism for characteristics of the mobile access network, and functions mainly provided by the PCC are: implementing policy control based on customize information of the user and service data stream based charging control.
The functional architecture of the 3GPP PCC is shown in FIG. 3. The Policy and Charging Rule Function (PCRF) includes policy control decision and charging by flow control functions. The PCRF provides network control functions such as detection on service data stream, gate control, QoS, and charging by flow (except for credit management) which are oriented to the Policy and Charging Enforcement Function (PCEF).
The PCEF includes service data flow detection, policy implementation, and charging by flow functions. The functional entity is located at the Gateway (GW). The PCEF provides service data flow detection, user plane traffic processing, trigger control plane session management, QoS implementation, service data flow measurement and interaction with a charging system. The Subscription Profile Repository (SPR) stores user subscription data. The OCS and the OFCS are online and offline charging systems respectively, wherein, the OCS includes a Customized Application Mobile network Enhanced Logic Service Control Point (CAMEL SCP) and a service data flow based credit control.
Both the fixed and mobile networks are deployed to implement respective resource control systems and service functions. Mobile users (dual-mode mobile terminal) access and visit services such as mobile securities transactions in the mobile network through the fixed network, and its networking scheme is shown in FIG. 4. The resource and admission control function entities (RACF/RACS) in the fixed network are connected to the Policy and Charging Rule Function (PCRF) in the mobile network, and the PCRF is connected to the mobile user information repository. FIG. 5 further illustrates a diagram of an interaction between RACF/RACS and a PCC, wherein, the RACF/RACS is connected to the PCC through an interface S9′, and the interface is mainly used for the information interaction between the RACF/RACS and the PCC.
As the RACF, the RACS and the PCC are largely different in terms of architecture, range of network, and involved types of nodes, the functions supported by the RACF, the RACS and the PCC under the existing technologies cannot implement the resource and admission control in the scene shown in FIG. 3. With the integration and open of different networks, there is an urgent need for harmonious resource control architecture to meet a service quality experience of the user.